1. Statement of the Technical Field
The invention is directed to heat pipes, and more particularly to multi-layer mesh wicks for heat pipes.
2. Description of the Related Art
Heat pipes are typically sealed, evacuated devices that transfer heat by evaporation and condensation of a working fluid. They are typically passive devices which require no external power for their operation. Conventional heat pipes generally operate by the introduction of heat into an evaporator section, which is usually located at one end of the heat pipe, where the introduced heat evaporates some of the working fluid. This increases the vapor pressure in the evaporator section and causes vapor to flow through the vapor space of the heat pipe towards a condenser section, typically at the other end of the heat pipe. Since the heat pipe is generally set up so that the condenser section is cooler than the evaporator section, the vapor condenses in the condenser section, releasing heat stored in the vapor. The condensed liquid is then returned to the evaporator, typically by capillary action within a wick structure within the heat pipe. Because of their high heat transfer efficiency and general overall simplicity, heat pipes are commonly used in various types of heat transfer applications. For example, heat pipes have been used for removing heat from an electrical circuit without the need for electrical power.
In general, one aspect of heat pipe design is the design of the wick. Typically, the wick is designed so as to provide high values for wick parameters such as thermal conductivity, capillary pumping pressure, and permeability to fluid flow. However, obtaining high values for these wick parameters using conventional methods is typically either economically or technologically impractical. For example, conventional wick technologies which provide high values for these wick parameters, such as sintered particle methods, are typically expensive and therefore economically impractical for many low-cost product applications. In the case of low-cost conventional wick technologies, such as groove and mesh (solid or woven) comprising wicks, a high thermal conductivity is typically difficult to achieve without significant reduction of fluid permeability or capillary pumping pressure.